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From: Naoya Horiguchi on 12 Aug 2010 04:10
This patch defines some helper functions to avoid race condition
on hugepage I/O. We assume that locking/unlocking subpages are
done in ascending/descending order in adderss to avoid deadlock.

Signed-off-by: Naoya Horiguchi <n-horiguchi(a)ah.jp.nec.com>
---
include/linux/hugetlb.h | 55 +++++++++++++++++++++++++++++++++++++++++++++++
mm/memory-failure.c | 24 ++++++++++++++++++++
2 files changed, 79 insertions(+), 0 deletions(-)

diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h
index c7b4dae..dabed89 100644
--- a/include/linux/hugetlb.h
+++ b/include/linux/hugetlb.h
@@ -312,6 +312,55 @@ static inline struct hstate *page_hstate(struct page *page)
return size_to_hstate(PAGE_SIZE << compound_order(page));
}

+/*
+ * Locking functions for hugepage.
+ * We assume that locking/unlocking subpages are done
+ * in ascending/descending order in adderss to avoid deadlock.
+ */
+
+/* If no subpage is locked, return 1. Otherwise, return 0. */
+static inline int trylock_huge_page(struct page *page)
+{
+ int i;
+ int ret = 1;
+ int nr_pages = pages_per_huge_page(page_hstate(page));
+ for (i = 0; i < nr_pages; i++)
+ ret &= trylock_page(page + i);
+ return ret;
+}
+
+static inline void lock_huge_page(struct page *page)
+{
+ int i;
+ int nr_pages = pages_per_huge_page(page_hstate(page));
+ for (i = 0; i < nr_pages; i++)
+ lock_page(page + i);
+}
+
+static inline void lock_huge_page_nosync(struct page *page)
+{
+ int i;
+ int nr_pages = pages_per_huge_page(page_hstate(page));
+ for (i = 0; i < nr_pages; i++)
+ lock_page_nosync(page + i);
+}
+
+static inline void unlock_huge_page(struct page *page)
+{
+ int i;
+ int nr_pages = pages_per_huge_page(page_hstate(page));
+ for (i = nr_pages - 1; i >= 0; i--)
+ unlock_page(page + i);
+}
+
+static inline void wait_on_huge_page_writeback(struct page *page)
+{
+ int i;
+ int nr_pages = pages_per_huge_page(page_hstate(page));
+ for (i = 0; i < nr_pages; i++)
+ wait_on_page_writeback(page + i);
+}
+
#else
struct hstate {};
#define alloc_huge_page_node(h, nid) NULL
@@ -329,6 +378,12 @@ static inline unsigned int pages_per_huge_page(struct hstate *h)
{
return 1;
}
+#define page_hstate(p) NULL
+#define trylock_huge_page(p) NULL
+#define lock_huge_page(p) NULL
+#define lock_huge_page_nosync(p) NULL
+#define unlock_huge_page(p) NULL
+#define wait_on_huge_page_writeback(p) NULL
#endif

#endif /* _LINUX_HUGETLB_H */
diff --git a/mm/memory-failure.c b/mm/memory-failure.c
index 1e9794d..e387098 100644
--- a/mm/memory-failure.c
+++ b/mm/memory-failure.c
@@ -950,6 +950,30 @@ static void clear_page_hwpoison_huge_page(struct page *hpage)
decrement_corrupted_huge_page(hpage);
}

+static void lock_page_against_memory_failure(struct page *p)
+{
+ if (PageHuge(p))
+ lock_huge_page_nosync(p);
+ else
+ lock_page_nosync(p);
+}
+
+static void unlock_page_against_memory_failure(struct page *p)
+{
+ if (PageHuge(p))
+ unlock_huge_page(p);
+ else
+ unlock_page(p);
+}
+
+static void wait_on_pages_writeback_against_memory_failure(struct page *p)
+{
+ if (PageHuge(p))
+ wait_on_huge_page_writeback(p);
+ else
+ wait_on_page_writeback(p);
+}
+
int __memory_failure(unsigned long pfn, int trapno, int flags)
{
struct page_state *ps;
--
1.7.2.1
--
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Prev: [patch 2/2] ip2: return -EFAULT on copy_to_user errors
Next: [RFC] [PATCH 2/4] dio: add page locking for direct I/O